Temperature sensors are often integrated in pressure-measuring cells, in order to compensate for the static temperature error. In generic pressure-measuring cells, this temperature sensor is typically arranged on the rear face of the ceramic; it can, however, also be contained inside a connected evaluation electronic device. If a pressure-measuring cell is in thermal equilibrium with its surroundings, the temperature dependence of the pressure measurement can be well compensated for by means of such a temperature sensor and a suitable processing of the measurement signal. However, temperature jumps can lead to significant measuring errors, which can hardly be compensated for using known methods. Especially in the case of ceramic pressure-measuring cells with a thin measurement membrane having a thickness of, for example, only a few 100 μm, with a medium-exposed surface of approx. 1 cm2 to 10 cm2, the temperature of the measurement membrane quickly follows the temperature of the medium the membrane is exposed to, whereas the heat transfer between the rear face of the counter body and the measurement membrane occurs very slowly, namely, via a circumferential joint between counter body and joint on the outer edge of the measurement membrane and then through the volume of the counter body to its rear face. Thus, a temperature measurement at the rear face of the counter body, in case of doubt, is always delayed.
The published German patent application DE 100 44 078 A1 discloses a pressure-measuring cell with two temperature sensors that are to be arranged at a distance in the direction of the expected temperature gradient. For this reason, the first temperature sensor is arranged at the measurement membrane that forms the front face of the pressure-measuring cell, where it can quickly follow the temperature changes of the medium, whereas the second temperature sensor is arranged at the rear face of the counter body of the pressure measuring cell and facing away from the measurement membrane. The first temperature sensor is arranged at the front face of the counter body, embedded in the joint and contacted via electrical transits through the base body.
A comparison between the temperature signals of both temperature sensors then enables the detection of a temperature gradient and a more accurate compensation of the effects that are caused by the temperature gradient, such as a curvature of the measurement membrane and/or the counter body, or changes in rigidities. The patent application mentions further that the temperature gradient can be established using the time derivative of the signal from the first temperature sensor.
However, as mentioned above, the joint between the measurement membrane and the counter body actually provides a significant thermal resistance, so that an additional temperature sensor at the front face of the counter body is, on the one hand, a significant improvement with regard to prior art; on the other hand, this temperature sensor is also exposed to the thermal influence of the counter body volume, so that, in case of quick temperature jumps, distortion is still to be expected. If a sealing ring is impacting the front face of the measurement membrane in the area of the joint, this can also have an influence on the temperature measurement value of the first temperature sensor, which can impair the temperature compensation.